Abortion parasite found in SA cattle herds

A South Australian beef cow. As many as one third of beef and dairy cattle herds in South Australia show signs of infection by the parasite Neospora caninum.
Photo by Michael Reichel.
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Neospora caninum parasites, as seen under a fluorescent microscope.
Image courtesy of Dr Fraser I Hill.
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Thursday, 28 April 2011

A parasite that is a major cause of miscarriage in cattle, sheep and goats worldwide may be present in one third of South Australia's cattle herds, according to new research from the University of Adelaide.

Although the number of cattle infected is low, the parasite can be found in a wide range of beef and dairy cattle herds and represents a threat to breeding, according to researchers with the University's School of Animal and Veterinary Sciences, Roseworthy Campus.

The culprit is a single-celled parasite called Neospora caninum. It causes spontaneous abortion in cattle, sometimes leading to "abortion storms" among herds. In Australia and New Zealand, losses are estimated to cost animal industries more than $100 million per year. There is currently no vaccine or effective treatment for N caninum infection in Australia.

Two PhD students with the School of Animal and Veterinary Sciences, Amar Nasir and Sasha Lanyon, have completed a survey of South Australian beef and dairy herds. They've tested almost 1000 blood samples from SA cattle.

"The results show that less than 3% of cattle are infected with the N caninum parasite, approximately 38,000 cattle in total. But the infection is widespread and occurs in about a third of all cattle herds - that's about 1400 dairy and beef herds across the state," says the study's supervisor, Professor Michael Reichel.

"The low level of parasite infection may be due to the sunny, dry climate in South Australia and could be good news for primary producers in this state. However, the widespread nature of the infection means that producers should be aware of the likelihood of abortions and the need to quarantine infected stock to prevent further spread of the parasite."

Methods of controlling the spread of the parasite include: diagnosis of infected cattle, quarantining those cattle and not breeding from them, and restricting the access of dogs and rodents (which can carry parasite infection) to cattle yards.

Professor Reichel says parasite infection is much more prevalent in overseas herds of cattle and buffaloes. PhD student Amar Nasir had previously conducted studies in dairy buffaloes in Lahore, Pakistan, which showed almost 55% N caninum infection in randomly selected blood samples.

"Infection from this parasite is a major problem across the globe," Professor Reichel says. "As well as the direct loss of stock from abortions, there are indirect losses such as the cost of rebreeding, reduced yields and the purchase of replacement animals.

"While South Australia fares much better than most other dairy and beef producers around the world, it's important to raise awareness of this parasite and the consequences it can have for cattle herds."

Mr Nasir has been conducting research in South Australia thanks to the support of the Higher Education Commission of Pakistan.

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